The invention relates generally to the field of cooling systems for buildings, and more particularly to the field of evaporative cooling systems in which ambient air is cooled by drawing it through a fine liquid mist or fog before it enters the building.
Evaporative cooling systems for buildings are known. Typical structures on which these systems are used are poultry and other animal houses, warehouses, etc. The concept of evaporative air cooling is based on the fact that the temperature of air drawn through a spray or a wet pad will be lower due to the transfer of heat from the air to the water, causing the water to evaporate.
In one of its simplest forms, buildings can be cooled by placing fogger nozzles to spray a fine mist of water in the interior of the building and using a fan system to draw air in a single direction through the building. This method is low in efficiency, and suffers the problem of accumulation of excess moisture in the interior, increasing the humidity and creating algae and bacteria problems. To improve on this method, evaporative cooling systems have been developed in which the fogger nozzles are placed exterior to the building. For example, Bohanon in U.S. Pat. No. 4,031,180 shows a system where pads are placed in an opening in the building wall and a water drip or infusion system is placed along the top of the pads to soak the pads thoroughly. Air is then drawn through the pads to be cooled. This system results in a large excess of water which must be captured and then recycled or discarded. Furthermore, because the pads are saturated, there are problems of algae build-up and pad deterioration requiring frequent pad replacement. Given that replacement pads for a single building may cost several thousands of dollars, this system is not desirable. Addressing the excess water problem, Van Huis in U.S. Pat. No. 3,965,691 teaches a system to be used in buildings having vents running the length of the building between the tops of the walls and the roof. Angled pads are mounted along the length of the roof and water is sprayed upward onto the underside of the pads. The water spray is controlled by timers such that the spray is intermittent rather than constant during the time period needed to cool the building in order to prevent oversaturation of the pads. Any run-off drips down to the outside of the building. For evaporative cooling systems to work in large buildings, it is necessary to draw a large amount of air through the building. This is usually accomplished by one or more large exhaust fans mounted into an end wall. The Van Huis system is not efficient since the air intake is spread over the entire length of the building, resulting in vast differences in the air flow rates through the pads at different points in the building, depending on the proximity to the exhaust fans. The portions of the Van Huis system far from the fans will have little cooling effect at all.
The evaporative cooling system developed and described herein eliminates the problems and shortcomings of the known systems. The invention is designed such that there will be no or only minimal water run-off and no pad saturation resulting in algae build-up or pad deterioration. This is accomplished by controlling the water droplet size and application zone, and by having an independent set of fogger nozzles operative only under extreme external conditions. The invention is designed so that the air flow is the same over all points of the intake system by placing the pads at positions of maximum distance from the air exhaust fans and maximizing the draw-through surface area at these focused locations, using a tunnel effect to maximize air and water contact.